This invention relates in general to wireless networks and more specifically to the optimization of the performance of a wireless connection. It involves optimizing the configuration parameters for the wireless networks.
A wireless network comprises at least one root bridge (hereinafter referred to as root node), a plurality of non-root bridges (hereinafter referred to as non-root nodes) and a plurality of client devices. Each bridge (root and non-root) is designed to connect two or more networks, which are typically located in different buildings. The non-root node may either be static or mobile in nature, while the root node is static.
Nodes connect hard-to-wire sites, noncontiguous floors, satellite offices, school, or corporate campus settings, temporary networks, and warehouses, wherein both the root node and the non-root nodes are static, i.e., they are located at fixed pre-determined positions. Alternatively, the nodes can be deployed in a mobile environment such as a train station, wherein a root node can be installed at the station and a plurality of non-root nodes are installed in a plurality of trains. These non-root nodes are mobile in nature. Passenger notebooks/PDAs within the train connect to the wireless network through the mobile non-root nodes. Similarly, a root node can be installed in a police head quarter while the non-root nodes can be installed in each policeman patrol car. The client devices such as PDAs and notebooks connect to the non-root nodes. Further, the root bridge is configured as an access point for functional flexibility.
Communication between the non-root nodes in a wireless network is established over a radio (or infrared) link. Each non-root node is connected to zero or more client devices such as a PDA, laptop or cell-phone. The communication between the non-root nodes is enabled by the root nodes, which are strategically placed to cover the area over which the wireless connectivity is to be established. The root nodes are connected together and to an Ethernet, using copper or optical fiber cables.
The nodes communicate by sending a data frame and waiting for an acknowledgement frame to arrive from the receiving node. This mechanism for communication is required due to the unreliable nature of the wireless medium. In such a medium, the sending node has an internal timer or clock that is started whenever a frame is sent. If no acknowledgement is received within a specified time interval, the clock times out and the frame is sent again.
The details of the above-mentioned communication are described in a family of specifications, referred to as 802.11, developed by the Institute of Electrical and Electronics Engineers (IEEE). The specifications provide details of over-the-air interface between a non-root node and a root node, two non-root nodes, and a non-root node and a client device.
The 802.11 communication protocol requires a certain time gap between two frames being sent from a node. Similarly, a time gap is required between the last frame of one node and the first frame of the second node. These time gaps are used for transmission control on the wireless network. The time gap values are computed by the root node and communicated to the non-root nodes. The timer values that are set include Slot time, and Inter-Frame Space (IFS) parameters such as Distributed Inter Frame Space (DIFS), Point Coordination Inter Frame Space (PIFS), Short Inter Frame Space (SIFS), and Extended Inter Frame Space (EIFS). Each node has system timers that store the values of these time gaps and are set by using a distance parameter configuration.
The distance parameter configuration requires knowledge of the maximum deployment distance, i.e., the maximum distance within which a non-root node should be able to access the root node. For deployment in a static wireless network, the distance parameter is configured by using the longest distance to a non-root node within the static wireless network. In a mobile wireless network, the distance parameter is configured by using the maximum reachable distance from the root node. This maximum distance is limited by the strength of the radio signals. Since the location of each of the non-root nodes in a mobile wireless network changes, the distance parameter configuration determined at the deployment time is not optimal. Also, the farthest non-root node may not be positioned at the maximum reachable distance at all times. For most of the time, the non-root nodes would be at distances less than the maximum reachable distance. Consequently, a non-root node waits for a time period that is longer than necessary, while communicating. For example, if the longest reachable distance for a root node is 10 miles, using the methods existing in the art, the distance parameter would be set to 10 miles, and the timer values would be adjusted accordingly. However, most of the non-root nodes would, at any time, be at distances less than 10 miles, with the farthest non-root node being at, for example, 5 miles from the root node.
The methods known in the art do not have any provision for the dynamic adjustment of the distance related timer values. As a result, the throughput of the wireless network decreases, since nodes use unnecessarily large values for inter-frame spaces and other timers.